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What's in a Color?

Institute for Exploration / Ocean Exploration Trust

When I found out that I would be on Nautilus for the Black Sea leg of the journey, I was excited!  I was fortunate to be a part of the expedition last year off the coast of Spain and Portugal and I really enjoyed the experience. Because of the name, I expected dark waters, but I was very surprised when I got my first glimpse of the Black Sea…


                                              The port of Sinop, Turkey (Black Sea)


  Growing up near the coast of the Gulf of Mexico, my experience with the clearer waters of the oceans has been limited.  The waters off of Galveston, Texas where we go to the beach are grey/green and visibility is limited.  If you visit the beaches further east off the coast of Florida, the waters are famed for their turquoise clarity.  When I went out to sea last year, I was amazed at the waters of the Atlantic Ocean off of the coast of Spain and Portugal.  I had never seen water that was such a deep royal blue and still so clear.  I was once again amazed this year because the waters of the Black Sea (instead of being black) are a blue green and equally as beautiful as any waters I have ever seen. 


                              The royal blue waters of the Atlantic Ocean off of Spain


  These observations raise a simple but important question, why are different bodies of water, different colors?  The answer lies in how light is absorbed and scattered. 


  When sunlight hits the water, green, red, orange, and yellow wavelengths of light are more strongly absorbed by the water molecules than the blue wavelengths.  We see what is left: the blue wavelengths.  The shade and hue then varies based on what particulates are suspended in the water.  Some particles increase the scattering of light and some can actually absorb light.  Both affect how we view the water as a whole. 


  One major light-affecting organism is phytoplankton.  Phytoplankton are tiny living things that live in various saline and fresh water environments.  Phytoplankton contain chlorophyll, the same pigment used by terrestrial plants in photosynthesis.  This pigment reflects green light so bodies of water with high concentrations of this organism appear more green than bodies of water with lower concentrations of them. There are also other light absorbing elements, but few have the potential to impact bodies of water the way phytoplankton do. 


  Beauty can be found in every ocean and sea, but there’s something much more exciting about understanding the science going on under the surface.